This invention concerns U-bolt saddle clamps of the type commonly employed in clamp pipe connections for exhaust systems of vehicles powered by internal combustion engines.
Conventionally, U-bolt saddle clamps are used, in which a U-shaped bolt member has threaded ends received through tubular openings formed in a saddle member, with central semi-circular cutouts complementing the radiused portion of the U-bolt, to enable clamping at a pipe section by tightening of locknuts received on the ends of the U-bolt protruding through the tubular portions of the saddle.
Many low-cost and effective designs for such U-bolt saddle clamps have been provided in the prior art for conventional exhaust system applications.
With the introduction of catalytic converters however, clamping the connections to the converter has presented a more difficult problem. The material employed in the the catalytic converter connections consists of relatively heavy walled stainless steel, which requires high clamping forces to compress properly, in turn imposing high stresses on the saddle used at such a connection. At the same time, the connection must be very tight to prevent leakage resulting in poor performance of the converter.
The conventional U-bolt saddle clamps have not had sufficient saddle rigidity to withstand the degree of tightening necessary for this application. Accordingly, relatively more rigid saddle clamp designs have been developed that are capable of withstanding the relatively high forces created during clamping.
Typical examples of high rigidity saddles are shown in U.S. Pat. No. 3,955,250 to Heckethorn; U.S. Pat. No. 4,040,152 to Gilgallon; U.S. Pat. No. 4,249,759 also to Heckethorn; and, finally U.S. Pat. No. 4,112,586 to Nothdurft.
In the Nothdurft U.S. Pat. No. 4,122,586 there is provided a one-piece developed sheet metal preform which is folded to form a double thickness saddle with a partially circular cutout on one side thereof, and a relatively straight edge at the fold between the opposite components. A pair of horizontal stiffener ribs are also provided. The U-bolt receiving tubular openings are formed by semicircular channels formed on either side of each of the folded sections. Adjacent each of the channels is an outer flange which is placed face-to-face and welded together in order to provide the unitary clamp structure. Spot welds are also applied in the overlying webs intermediate to the formed channels.
The resultant saddle clamp, however, is relatively difficult to form due to the one-piece construction and, in addition, the outer flanges created excessive radial dimensions which in turn creates problems of sufficient clearance at installation.
Also, the spot-welds of the flanges and the intermediate webs of the saddle are often imperfectly made since the welding is done as the halves of the saddle preform are compressed together in the welding apparatus, and upon release of the pressure a slight spring-back may produce arcing, and separation of the welds or at best incomplete welds.
Most importantly, the rigidity of Northdurft and the other designs has been found to be excessive, in that if the pipe connection is out-of-round or otherwise varies in size or shape, the stiffness of the saddle section does not allow conforming deflection thereof. This results in reduced radial deflection along the line of contact, and less reliable sealing of the joint.
In U.S. Pat. No. 3,055,072 to Brown there is disclosed a two-piece flangeless saddle design, in which channels are formed on either side of each piece, which are abutted and welded to form the tubular design. However, the web sections are of inadequate rigidity for application to high force applications heretofore described. Furthermore, weld flash along the edge has been found to reduce the clearance in the circularly shaped openings of the U-bolt. If a smaller U-bolt is used or larger channel openings resorted to, non-standard parts are required, increasing costs.
Accordingly, it is an object of the present invention to provide a saddle construction for a U-bolt type clamp which is of sufficient rigidity to withstand the stresses imposed by a high degree of tightening for the converter clamping applications described, but which rigidity is not so high as to preclude some deflection of the saddle clamp necessary to accommodate variations in the pipe size and hardness.
It is another object of the present invention to provide a simple and low cost construction of the saddle for a U-bolt clamp.
It is yet another object of the present invention to provide a saddle clamp construction in which the radial dimension is minimized in order to provide maximum clearance at assembly of the U-bolt clamp to the pipe connection.
It is another object of the present invention to provide such a saddle construction and method of manufacture in which spot welding of the components may be achieved with a high degree of reliability.